Resistance device



Aug. 14, 1934.

A. L. PUGH, JR

RESISTANCE DEVICE Filed March 28,A 1929 ATTORNEY A Patented Aug. 14, 1934 UNITED STATES PATENT OFFICE RESISTANCE DEVICE Application March 28, 1929, Serial No. 350,594

19 Claims.

This invention relates to electrical resistance devices.

' One of the objects thereof is to provide a practical and efficient device of the above nature. Another object is to provide a device of the above ynature which is simple in construction and inexpensive to manufacture. Another object is to provide a practical device of the above nature aifording a high resistance and of small size, adapting it for use in the construction of telephone plugs. Another object is to provide a practical art of making resistance devices of the above nature which may be carried out conveniently and reliably. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists inthe features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and in order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which is shown one of various possible embodiments of my invention,

Figure 1 is a longitudinal section through a telephone plug, showing the disposition of my resistance device therein and its particular manner of mounting;

Fig. 2 is a similar cross section of a portion of the plug taken at right angles to the section .f'hou'n in Fig. 1, with the resistance device shown in elevation.

Fig. 3 is an elevation of the plug as shown in Fig. l with the insulating sleeve removed;

Fig. Il is an enlarged longitudinal section of the resistance device;

Fig. 5 is a still more enlarged cross section taken on line 5-5 of Fig. 4; and

Fig. 6 is a similary cross section taken on line 6 6 of Fig. 4.

Similar reference characters refer to similar parts throughout the specification and the drawing. l

Before describing the invention in detail, it may here be noted that radio receiving apparatus is often installed in hotels, apartment houses, and the like, at some central point, as in the lobby. From the receiver, output connections are made in the different rooms and at different points throughout the build-ing, which connections terminate in telephone jacks into any one ci which a' telephone head set or loud speaker may be plugged.

Such an arrangement has not always proved satisfactory for the reason that, Whereas the output of the apparatus may be adjusted to produce a volume suitable for either loud speaker or head set, such adjustment does not satisfactorily permit of the use of both. A volume output suitable for loud speaker is excessive for head sets, or volume control suitable for head sets is to Weak to give good results with a loud speaker.

'My invention solves this diiliculty` in a satis- 55 factory and practical manner by the employment of a resistance unit built into a telephone plug. By the use of such a plug, head sets may be jacked into a jack connection and satisfactory results may be had even though the receiving apparatus is controlled for loud speaker volume. In carrying out my invention, I incorporate a high resistance unit, as, for example, one having a reother unit of any desired resistance value be substituted, should conditions make such a change desirable. As I preferably mount my resistance .unit within the shank of the plug, the unit itself must be particularly adapted to the purpose. To this end it must be of small size and yet have high resistance.

By reason of their particular form and mode of construction, together with the arrangements provided for'their mounting, resistance devices made in accordance with my invention successfully meet the requirements mentioned above.

Referring to the drawing for a detailed description, and first to Fig. l, l0 represents generally 90 a telephone plug of standard construction, in which a brass shank 11 is threaded at l2 to receive an insulating sleeve 13. The sleeve 13 may be made of bakelite or other suitable insulating material. At 14 and 15 are shown brass contact 95 members, furnished with screws 16, by means of which connection may be made to the tips of a telephone cord. 17 is an insulating washer separating the faces of the two contact members 1,4 and 15. At 18 is shown a plug tip of the usual 100 form separated from the end of the shank 11 by an insulating washer 19.

In the standard plug, the tip, the shank, and the contact members are usually drawn together by means of a screw whose head is in contact 10 with the inside circuit contact member, as 14, and which is provided with threads upon which the tip 18 is secured. In such a construction, when the tip is turned up as far as it will go, the a parts are held rigidly in position. lo

the screw just mentioned a resistance element,

generally denoted by the numeral 20, which is provided with threaded terminal members 21 and I 22. Each of these members is formed to contain a socket space, as 23, terminating'at its base in a reduced portion 24. A hollow 25, in axial alinement with the socket 23, is formed as an extension of said socket of relatively small diameter. A porcelain insulator 26 is held between the two terminal members which fit over and are held tightly engaged with the ends thereof. The insulator member 26 is provided with a capillary passage 27 having a diameter on the order of .024. In this passageway is mounted a resistance element 28 having a diameter of approximately .022". Such a resistance element preferably consists of a fine fiber or filament of glass having. a film-like deposit or layer of a conducting material, such as carbon or graphite, adhering to its surface.. It will be noted that the ends of the member 28 extend beyond the ends of the porcelain tube through the reduced base of the socket 24 and into the hollow 25 at each end.

It will be understood that in the construction .of this resistance device requiring high resistance and small size, resistance elements of small size a're preferably used; in fact, allof the parts ought to have their dimensions reduced to a practical minimum. This is made possible by use of the glass fiber resistance referred to, but in using such a brittle element, great care must be taken in the assembly of the resistance unit, and the parts must be held in such a way as to insure nonbreakage of the said element subsequently. In order to accomplish this end, I have devised the following art or method of manufacture.

The porcelain tube is of a diameter only about .002" smaller than the interior diameter of the terminal members. In order to insure a tight fit, I have found it expedient to interpose a layer or film of' softer metal between the overlapping surfaces of tube and terminal. IThis is accomplished by tinning the'inside ofthe socketV of the terminal with pure tin, soft solder, or the like.

In the drawing the layer of tin is shown at 29 in greatly exaggerated thickness.

I then fill the tapered base of the socket with type metal, indicated at 30. By the term type metal, I designate such alloys as suil'er little change in volume under change of physical condition, as from a fiuid or semi-fluid to a solid state, the aforesaid change, however, being a slight expansion, so that upon freezing the metal contracts inwardly against anything included within it. I do not confine myself to any particular alloy having these characteristics. This inward contraction upon expansion of the metalr is due to reaction against the walls of the mold; the sockets 23 of the terminals act as molds in the manufacture of the device as will now be pointed the porcelain tube may be easily inserted therein.

The type metal filling is preferablyrun into the terminal member while hot, but it may bf;

In carrying out my invention, I substitute for i found desirable in some cases to insert cold a plug of type metal of the proper shape and size to be pressed down into the base of the socket and the hollow continuation thereof.` Further, the said plug may be first prepared by drilling axially, so that when the parts are assembled the said resistance element will be received within the type metal plug prior to the application of heat to the terminal.

The parts having been assembled as described, the terminal member is permitted to cool. The shrinkage of the walls of the socket is prevented from doing injury to the porcelain tube by the compression of the `relatively soft film of tin interposed between them. At the same time, the type metal closes in firmly around the end of the tube and about the resistance element 28, making good electrical contact with the nlm of resistance material disposed upon the surface thereof. When these steps have been completed, the other terminal member is similarly heated and the parts united in the manner just described. As the film of tin is under compression during the cooling of the terminal member, it is made to fit snugly about the porcelain tube, thus insuring an airand moisture-proof joint of high mechanical strength.

The resistance unit 20, made as described, is now assembled in the shank of the plug by shoving itA through from one end thereof. To prevent its making electrical contact with the walls of the shank and to protect it mechanically, a sleeve of paraffin paper is interposed between the two parts, as shown at 32. The tip 18 is threaded upon the outer end of the resistance unit, and at the other end a particular form of nut 33 is em-I ployed to draw the parts together. This nut has a rounded contact surface, as at 34, which makes substantially line engagement with the edge of the opening in the circuit contact member i4. By employing a nut having this feature, alinem'ent of the resistance unit within the shank is assured and without strain to said unit. This feature is important, for were the parts drawn together by a nut having the usual fiat surface, breakage of the porcelain of the unit would be likely to follow, and the alinement of said unit would be uncertain, so that short circuits might occur.

From the foregoing it will be seen that this invention isv one well adapted to attain the ends and objects hereinbeforel set forth in a thoroughly practical manner.

As many possible embodiments may be made of the mechanical features of the above invention, and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth or shown in the accompanying drawing is to be interpreted as -illustrative and not in a limiting sense.

I claim:

1. A telephone plug having a body portion, a:

hollow shank, a tip insulated from said shank, and a resistance unit of predetermined ohmic value encased within said shank and having electrical contact with said tip.

2. In electrical resistance devices, in combina- 3. In electrical resistance devices, in combination, a telephone plug having a shank, a connector in electrical contact therewith, a tip, a connector spaced apart from said tip, a resistance unit disposed Within said shank and providing a conductive path of high resistance between said tip and said second connector, and an insulating sleeve interposed between said resistance means and said shank.'

4. In resistance devices, the combination with a telephone plug having a shank, circuit-connecting means disposed adjacent oneiend of said shank and insulated therefrom, a tip disposed at the other end of said shank and insulated therefrom, of resistance means comprising an insulated elongated filament adapted to be received longitudinally within said shank, and means for removably connecting one end of said resistance means with said circuit-connecting means and the other end of said resistance means with said tip.

5. In resistance devices, in combination, a telephone plug having a tubular shank, contact members disposed at opposite ends of said shank, and an elongated resistance unit removably mounted longitudinally within said shank and having threaded terminal portions adapted to be secured in electrical contact with said contact members.

6. In resistance devices, in combination, a telephone plug having a-tubula-r shank, a resistance unit adapted to be mounted within said shank in substantial alinement with the axis thereof and having threaded terminal members extending beyond the ends of said tubular member, a contact member adapted to be threaded upon one of said terminal members in substantially fixed alinement with the axis of said shank, a second contact member adapted to be secured to the other of said terminal 'members and a nut adapted to engage the threads of said other terminal member and have engagement with said second contact member along a universal bearing surface.

'7. In resistance devices, in combination, a telephone plug having a tubular shank, a resistance unit adapted to be mounted longitudinally within said shank in substantial alinement with the axis thereof and having threaded terminal members extending beyond the ends of said shank, a contact member adapted to be threaded upon one of said terminal members in substantially fixed alinement with said tubular member, a second contact member adapted loosely to fit over the other of said terminal members, and a nut adapted to engage the threads of said other terminal member and to make substantially line contact with said second contact member.

8. In resistance devices, in combination, a telephone plug having a tubular shank, a resistance unit adapted to be mounted within said shank in substantial alinement with the axis thereof and having threaded terminal members extending beyond the ends of said shank, a contact member adapted to be threaded upon one of said terminal members in substantially fixed alinement with said tubular member, a second contact member adapted loosely to fit over the other of said terminal members, and a nut adapted to engage said other terminal member and having a rounded surface for engagement with said second contact member to hold said'resistance unit in its position of fixed alinement and without bending strain.

9. A resistance comprising a pair of metal terminals of hollow cylindricalform at one end and. having external screw threads at the other end, a porcelain tube in said hollow portions connecting said terminals mechanically, a layer of compressed low melting point alloy between said hollow portions and said porcelain, and a resis tance conductor in said tube in electrical connection with said terminals.

l0. A construction for resistors comprising an integral Vmetal socket with an elongated shank having a reduced bore in said shank, a porcelain tube having a relatively small bore, said porcelain tube substantially fitting said socket, a lm of compressed metal between said socket and said tube, a filament resistance in the bore in said tube extending into the bore in said shank, and metal of low melting point in the bore in said shank embedding said lament. a

1l. A construction for resistors comprising an integral metal socket with an elongated shank having a reduced bore in said shank, a porcelain tube having a relatively small bore, said porcelain tube substantially fitting said socket, a filament resistance in the bore in the tube and extending into the bore in said shank, and metal lof low melting point in the bore in said shank embedding said lament.

12. A resistance device comprising a porcelain tube, a resistance rod including carbonaceous substance received in said tube, an integral metallic screw and cup blocking one end of said tube and the cup part receiving one end of said rod, and a substance adhering to said porcelain and opposed between said cup and said tube, and additional initially conformable metallic substance received in the cup and interposed between the terminal and the rod to make a good electrical connection.

13. A resistance device comprising an insulating tube, a resistance rod including carbonaceous substance received in said tube, an integral metallic screw and cup blocking one end of said 115 tube and the cup part receiving one end of said rod, and a substance adhering to the insulating substance and opposed between said cup and said tube, and additional initially conformable metallic substance received in the cup and interposed between the terminal and the rod to make a good electrical connection.

14. A resistance device comprising an insulatbing tube, a resistance rod including carbonaceous substance received .in said tube, an integral metallic screw and cup blocking one end of said tube and the cup part formed for the reception of one end ofsaid rod, means associated with said cup to secure a tight connection between said cup and said tube to prevent relative movement therebetween, and means received in said cup for insuring non-microphon'ic electrical connection between said cup and said rod comprising metal in a state of compression and enveloping said rod.

15. A resistance device comprising an insulating tube, a resistance rod including carbonaceous substance disposed within said tube, an electric terminal disposed at one end of said tube including a threaded part capable of connection to complete an electric circuit therethrough, means connecting said terminal to said tube, an electric terminal disposed at the other end of said tube including a threaded part capable of connection to complete an 'electric circuit 145 therethrough, means for connecting said secondmetallic means disposed between and intimately enclosed by said' tube said other terminal and said rod so that the i'ull pressure-exerting torce of said metallic means is applied against said rodand said other terminal to form a non-microphonic electrical connection between said other terminal and said rod.

`16. A resistance device comprising an insulating tube, a resistance rod including carbonaceous substance disposed within said tube, means disposed at one end of said tube adapted to form a releasable interiitting connection with a stationary metallic member, and means disposed at the other end of saidtube adapted to form a tight connection with a flexible wire, one of said means being in electrical connection with one end portion of said rod and the other of said means comprising an electric terminal, means for connecting said terminal to said tube, and pressure-exerting metallic means disposed between and intimately enclosed by said tube,v said terminal and said rod so that the full pressure-exerting force of said metallic means is applied against said rod and said terminal to form a non-microphonic electrical connection between said terminal and said rod.

17. A resistance device comprising an insulatconnection with one end portion of said rod and the other of said4 means comprising an electric terminal, means for connecting said terminal to said tube, and pressure-exerting metallic means disposed between and intimately enclosed by said tube said terminal and said rod so that the full pressure-exerting force of said metallic means is applied against said rod and said terminal to form a non-microphonicV electrical connection between said terminal and said rod.

y 18. A resistance device comprising an insulating tube, a resistance rod including carbonaceous substance disposed within said tube, means disposed at one end of said tube adapted to form a releasable interiltting connection with a stationarymetallic member, and means disposed at the other end oi said tube adapted to form a tight connection with a flexible wire, one of said means being in electrical connection with one end portion of said rod and the other of said means comprising a metallic cup, means connecting said cup to said tube,'and pressure-exerting means disposed between and intimately enclosed by said tube said cup and said rod so that the full pressure-exerting force of said metallic means is applied against said rod and said cup to form a non-microphonic electrical connection between said cup and said rod.

19. A resistance device comprising an insulating tube, a resistance rod including carbonaceous substance disposed within said tube, means disposed at one end of said tube adapted to form a releasable intertting connection with a stationary metallic member. and means including a threaded part disposed at the other end of said tube adapted to form a tight connection with a flexible wire, said mst-mentioned means being in electrical connection with one end portion ot said rod and said second-mentioned means including a metallic cup, means for connecting said cup to said tube, and pressure-exerting means disposed between and intimately enclosed by said tube said cup and said rod so that the full pressure-exerting force of said metallic means is applied against said rod and said'cup to form a non-microphonic electrical connection between said cup and said rod. l

ALEXANDER L. PUGH, Ja. 

